Comparability
Universe changes compromise the comparability of this variable over time. In 1983 and 1988 this question was asked of sample adults 18+. In 1992, this question was included as part of the Youth Risk Behavior Supplement and was asked only of sample persons who were age 12-21 at the time of the original NHIS interview. Because the Youth Risk Behavior Supplement was conducted two months after the original NHIS interview, some respondents were 22 at the time the supplement was administered.
